Micro-current sensing auto-adjusting heater system for eye-shield

ABSTRACT

Eye-shield condensation prevention system for use in a ski goggle, dive mask, medical or testing face shield or the like, that prevents undesirable hot spots on the eye-shield and maintains constant heat, with the ability to compensate for variations in resistance encountered from one eye-shield region to another, and/or one eye-shield to another, comprising a power source, a pulse-width modulator, a microcomputer, a heating element, and a sensing circuit. The microcomputer uses the sensing circuit to sense voltage and determine a value of resistance of the heating element. The microcomputer then uses this value to adjust the duty cycle of the pulse-width modulator, and may employ a two-dimensional table in assisting calculation. Multiple pulse-width modulators may be employed that correspond to a plurality of eye-shield regions and a corresponding plurality of heating elements.

CROSS-REFERENCE TO AND INCORPORATION BY REFERENCE OF RELATED APPLICATION

This application is a continuation-in-part of prior co-pending U.S.patent application Ser. No. 14/040,683, to Cornelius, for MultiregionHeated Eye-shield, filed 29 Sep. 2013, Publication No.US-2014-0027436-A1 (hereafter also referred to as the “ParentApplication”), which is a continuation-in-part of U.S. patentapplication Ser. No. 13/397,691, to Cornelius, for PWM Heating Systemfor Eye-shield, filed 16 Feb. 2012, which issued as U.S. Pat. No.8,566,962, issued 29 Oct. 2013 (hereafter also referred to as “the PWMApplication”). This application claims the benefit and the priority ofthe Parent Application and the PWM Application. The Parent Applicationand the PWM Application are hereby incorporated by reference in thisapplication.

FIELD OF INVENTION

This invention relates to heating systems employing resistive heatingelements on eye-shields, and more particularly to improved heatingsystems for portable anti-fog eye-shields able to be worn on users'heads, to enable consistency in heating from one portion of aneye-shield to another portion of the eye-shield and/or to enableconsistent heating from one eye-shield to the next eye-shield.

BACKGROUND OF THE INVENTION

It is often desirable to use sport goggles, dive masks and other highlyportable transparent eye-protecting shields in environments involvingconditions which contribute to condensation build-up on the eye-shieldand where even momentary impairment of vision by fogging would beproblematic. When the temperature of such an eye-shield has droppedbelow a dew-point temperature, i.e., the atmospheric temperature belowwhich water droplets begin to condense and dew can form, fogging hasoccurred and has obstructed vision.

A common characteristic of such portable eye-protecting shields is thefact that they are lightweight enough to be worn on a user's head andare positioned relatively closely to a user's face such that the user'sbreath and body heat exacerbates fogging conditions. Examples offog-prone sport goggles intended for use during winter activities haveincluded goggles for downhill skiing, cross-country skiing,snowboarding, snowmobiling, sledding, tubing, ice climbing and the like,and are widely known and widely utilized by sports enthusiasts andothers whose duties or activities require them to be outside in snowyand other inclement cold-weather conditions. Examples of fog-pronegoggles and eye-shields used in military or tactical environments,including cold weather and other environments, have included ballisticsgrade goggles used in military or hunting operations, goggles for use incorrectional facilities, protective eyewear and goggles for use inpolice work, crowd control, riot control, or swat operations. Examplesof fog-prone dive masks have included eye and nose masks independent ofa breathing apparatus, as well as full-face masks in which the breathingapparatus is integrated into the mask. Examples of fog-proneeye-protecting shields have included a face shield that a doctor ordentist would wear to prevent pathogens from getting into the user'smouth or eyes, or a transparent face shield portion of a motorcycle orsnow-mobile helmet. Fogging that impairs vision is a common problem withsuch goggles, dive masks and eye-protecting shields.

There have been various conductive apparatus devised for preventingcondensation build-up on eye-shields for eye-protecting shields. Thepurpose of such prior conductive apparatus has been to provideeye-shields that may be maintained free of condensation so that userswould be able to enjoy unobstructed vision during viewing activities.However, without apportionment of the heater on the irregularly-shapedeye-shield lenses of these apparatus, such eye-shields have been subjectto problems of creating hot spots on the irregularly-shaped lenses andhave not provided for customizable heating of the lenses.

Thus, there have been developed a newer system as disclosed inco-pending U.S. patent application Ser. No. 14/040,683, to Cornelius,for Multiregion Heated Eye-shield, filed 29 Sep. 2013, Publication No.US-2014-0027436-A1 (hereafter also referred to as the “ParentApplication”), which is a continuation-in-part of U.S. patentapplication Ser. No. 13/397,691, to Cornelius, for PWM Heating Systemfor Eye-shield, filed 16 Feb. 2012, which issued as U.S. Pat. No.8,566,962, issued 29 Oct. 2013 (hereafter also referred to as “the PWMApplication”). This newer system has made use of apportioned heaters onan eye-shield, but there has developed the potential problem that theresistivity of the heater from one portion of the heater to anotherportion of the heater on the eye-shield may be different, and this wouldalso lead to variations in heating across the eye-shield. Further, anadditional problem associated with a thin-film heater for eye-protectingshields has been the variations of resistance in the heaters encounteredfrom one eye-shield to another eye-shield.

Before the Parent Application and the PWM Application, no prioreye-shield condensation prevention system had taught a system foremploying an apportioned thin-film heating system for evenly heating anirregularly-shaped eye-shield, or alternatively for customized heatingof such an eye-shield according to a lens heating profile. Accordingly,the undesirable effects on even, uniform, or otherwise expected,heating, resulting from varied resistance of a thin-film heater acrossan eye-shield, or from one eye-shield to the next, had not beenappreciated until the Parent Application and the PWM Application hadbeen implemented.

The defogging ability of a thin-film heater on an eye-shield isdetermined by the amount of power supplied to the thin-film heater, thetime the power is supplied, and the electrical resistance of thethin-film heater. Thus, variations in resistance of such thin-filmheaters have resulted in variations of heating temperatures resulting onthe eye-shields, or eye-shield regions, themselves. These variations ofresistance have resulted primarily from difficulties experienced inapplying the thin-film heating elements uniformly across the eye-shieldsurfaces, and from difficulties experienced in applying the thin-filmheating elements consistently uniformly from one eye-shield to another.Also, different methods applying thin-film heating elements toeye-shields may lead to difference resistance values obtained. Thus, theuneven and inconsistent application of thin film heating elements hascreated variations in resistivity across the eye-shield regions, and asa result, variations in heat supplied by the thin-film heaters on therespective eye-shield regions.

Such variations in thin-film heater thickness could result, for example,when a thin-film heater has been applied from a single source that isvariable in thickness from one region of the source to another region ofthe same source (e.g., a single roll of PET with an uneven thin-film ofIndium-Tin-Oxide (ITO) thereon due to uneven application by sputtering),or perhaps when each region comes from a different source of thin-filmheater material (e.g., from two different rolls of PET with varyingthickness thin-film heaters on one roll relative to the other roll).Either way, the problem is the same which has led to uneven, orotherwise undesirable, heating characteristics. Accordingly, there havebeen variations of resistance encountered from one region of aneye-shield to another region of the same eye-shield, or from oneeye-shield to another eye-shield in a group, or batch, of eye-shields.

Prior goggles and eye-shields with electronic systems have beenprimarily used in environments requiring a high degree of portability,that is, where a power source for powering the electronics for thedevice has been advantageously carried on a strap for the goggle or onthe goggle itself, as shown and described in co-pending U.S. patentapplication Ser. No. 13/519,150, by McCulloch et al., for Goggle withEasily Interchangeable Lens that is Adaptable for Heating to PreventFogging.

Some examples of disclosures providing for heating of goggle lensesinclude the following: U.S. Pat. No. 4,868,929, to Curcio, forElectrically Heated Ski Goggles, comprising an eye-shield with embeddedresistive wires operatively connected via a switching device to anexternal power source pack adapted to produce heating of the eye-shieldfor anti-fog purposes. The Curcio disclosure does not teach even heatingof a lens, or alternatively customized heating of a lens, by employing acertain configuration of thin-film heating material on the lens.Accordingly, Curcio likewise does not teach even and consistent heatingof multiple regions of a single lens. Nor does Curcio teach even andconsistent heating of one eye-shield to the next eye-shield of aplurality of eye-shields.

US Patent Application No. 2009/0151057A1 to Lebel et al., for ReversibleStrap-Mounting Clips for Goggles, and U.S. Pat. No. 7,648,234 to Welchelet al., for Eyewear with Heating Elements, disclose use of thin-filmheating elements used for heating an eye-shield with a push-buttonswitch for turning on power from a battery carried on an eyewear band oreyewear arm. Neither Lebel et al. nor Welchel et al. teach even heatingof an irregular-shaped lens, or alternatively customized heating of thelens, by employing a certain configuration of apportioned thin-filmheating material on the lens. Accordingly, neither Lebel nor Welchel etal. teach even and consistent heating of multiple regions of a singleeye-shield or consistent heating of one eye-shield to the nexteye-shield of a plurality of eye-shields.

U.S. Pat. No. 5,351,339 to Reuber et al., for Double Lens ElectricShield, recognizes the problem of un-even heating where anelectro-conductive film is deposited on an irregular-shaped visor lensand proposes a specific bus bar configuration (electrodes 50 and 60)that addresses the problem of making the distance between electrodessubstantially the same for fairly uniform flow of electrical currentacross the electro-conductive film. However, Reuber et al. does notdisclose even heating of a lens, or alternatively customized heating ofthe lens in accordance with a heating profile, by employing a certainconfiguration of apportioned thin-filmed heating material on the lens.Further, the eye-shield of Reuber et al. was more uniform than that of aconventional goggle having a cutout portion adapted to fit over thebridge of a user's nose. Accordingly, the configuration of the electrodebus bars of Reuber et al. would not suffice for a more conventionalgoggle lens configuration. Still further, Reuber does not teach even andconsistent heating of one region of an eye-shield to the next region ofthe same eye-shield, or consistent heating among multiple eye-shields,through the use of an apportioned thin-film heater.

Thus, variations in the thickness of thin-film heaters applied to heateye-shields to prevent fogging have led to uneven heating over theentire surface of an irregular-shaped eye-shield, and in particular overmultiple regions of a single irregular-shaped eye-shield or multipleirregular-shaped eye-shields. Goggles and dive masks, and theireye-shields, are manufactured with an irregular shape required tomaintain a position close to the face of the wearer and allowing cutoutsfor the nose and extended edges for peripheral vision. While variousgeneral attempts to evenly heat an eye-shield across its entire surfacehave been made with serpentine wires included on, or within, eye-shieldlenses, as for example in published US Patent Application No.2008/0290081A1 to Biddel for Anti-Fogging Device and Anti-FoggingViewing Member, and U.S. Pat. No. 4,638,728 to Elenewski for VisorDefroster, even heating of an irregular-shaped eye-shield, or customizedheating of such an eye-shield, with an apportioned thin-film heater, hasnot been taught in the prior art. Similarly, the prior art has notdisclosed even and consistent heating of one region of an eye-shieldrelative to another region of the same eye-shield, or consistent heatingfrom one eye-shield to the next, despite variable thicknesses ofthin-film elements used.

The goggle of Lebel et al. would be susceptible to hot spots, andtherefore using such a device in a limited battery-powered applicationwould have unduly discharged the battery. The reason for the hot spotshas been because the electrical resistivity between the electricalconnections across the resistive elements on the eye-shield has beengreater or lesser at different locations on the eye-shield such that theamount of electrical current consumed in the areas with less distancebetween terminal connections is greater and the amount of electricalcurrent consumed in areas with greater distance between the terminalconnections is less. For example, where the terminals are on either sideof the lens in a resistive wiring application, there have been problemswith evenly heating the lens since the distance the wire has had totravel from one terminal to the other has been greater for those wirestraveling over the bridge of the nose and down under the eyes than otherwires that travel the shorter distance across a central portion of thelens. To overcome fogging conditions enough power must be applied toovercome the fog in the areas with the greatest distance between theterminal connection points, causing the shorter distance areas tooverheat, which in turn has wasted power. Thus, the problem has resultedin limited usefulness of heating of goggle eye-shields. Because of theirregular shape of eye-shields, these problems have existed whether onehas considered resistive-wire applications or resistive-filmapplications.

Still another problem associated particularly with goggles and divemasks is the amount of space provided between the eye-shield portion ofthe device and the user's face. Where insufficient space has beenprovided, the wearing of corrective lens eye glasses within the goggleor mask has been prohibited. Further, where excess distance has beenprovided between the shield portion of the device and the user's eyes,the ability to incorporate corrective lenses into the goggle or maskeye-shield itself has been prohibited. Increased distance between theuser's eyes and the eye-shield has improved anti-fogging capability intypical air-flow dependent anti-fog goggles, however, locating theeye-shield at such a great distance from the user's eyes to facilitateanti-fogging has made corrective goggle lenses ineffective forcorrecting vision, because excessive lens thickness would have beenrequired to accommodate the higher degree of curvature necessary in thelens to make the necessary vision correction. Thus, what has been longneeded in the corrective lens goggle, or dive mask, art is a technologythat would both permit a corrective eye-shield lens to be sufficientlyclose to the user's eyes to function properly from a vision correctionperspective, but which is also capable of effective fog prevention.Thus, there has developed a need to balance regions of eye-shields toenable even heating of eye-shields across the entire eye-shield surfacewithout excessive use of power or hot spots and without excessive spacebetween the user's eyes and the eye-shield itself for vision correctionlens purposes.

SUMMARY OF THE INVENTION

The multiple-region eye-shield of the present invention provides athin-film conductive heating element on the eye-shield or lens surfacethat is divided into multiple regions, for example regions according toirregular and differently-shaped portions of the lens such as directlyover the bridge of the nose as compared to directly in front of theeyes, to enable even, or alternatively custom, heating of suchdifferently-shaped or sized regions.

In accordance with an aspect of the invention, there is provided aneye-shield adapted for use with a powered circuit having a givenvoltage, for preventing fogging of the eye-shield and for preventing hotspots on the eye-shield. The eye-shield in accordance with this aspectof the invention comprises: An optically-transparent substrate adaptedfor protecting at least one of a user's eyes and adapted for defining atleast a partially-enclosed space between at least one of the user'seye's and the substrate; and a plurality of electrically conductiveregions of optically-transparent, electrically-resistive thin-filmconductive heating material on the substrate. Preferably, in accordancewith this aspect of the invention, an eye-shield capable ofsubstantially even heating across the entire eye-shield is provided,even if the eye-shield is an irregularly-shaped eye-shield.

Preferably, in accordance with this aspect of the invention, the numberof conductive regions and the size of each conductive region isdetermined in accordance with predetermined power densities for theregions of an irregularly-shaped lens. In accordance with one embodimentof this aspect of the invention, the power density of each region ispreferably the same as the power density of each other region. Inaccordance with another embodiment of this aspect of the invention, thepower density of at least one region would be different than the powerdensity of another region.

The number of the plurality of regions and the size of each region onthe substrate may, or may not, be made in accordance with a heatingprofile. In this regard, a heating profile could be simply anunderstanding on the part of the designer of the lens that he or shewould like even heating, to the degree feasible, across the lenssubstrate as in accordance with this aspect of the invention. Or, inaccordance with another aspect of the invention, an understanding, orprofile, may involve custom heating of an eye-shield, as for example maybe the case for a snowboarder as compared to a skier. A heating profilemay typically be used where one or more parts of the eye-shield are tobe intentionally made warmer than other parts of the eye-shield (e.g.,where one side is warmer than another, or the edges are warmer than themiddle of the eye-shield). Thus, for example, in the case of asnowboarder, one side of the lens corresponding to the forward foot ofthe snowboarder may require more heat since the snowboarder typicallystands more sideways while going down a hill. In accordance with eitherthe even heating aspect of the invention, or the custom heating aspectof the invention, a heating profile may include a more detailed writtenprofile including one or more of defined lens heating material regions,identification of size and shape of lens heating material regions,desired regions of relative increased heating, or decreased heating, andidentification or calculation of respective region power densities.Thus, the heating profile may be very simple, even just understood, ormore complex and even written, and determines whether balanced, or even,heating is desired from one conductive region to the next across theeye-shield, or whether a custom profile of full or proportional heatingfor each of the regions would be more desirable for a given eye-shieldconfiguration or purpose. The invention may be used to produce bothregular and more irregular-shaped eye-shields that are evenly heated, oralternatively in accordance with a custom heating profile.

In one embodiment of the invention, each conductive region is isolatedby an electrically conductive area on the eye-shield substrate. Thisembodiment of the invention enables a designer and manufacturer toprovide for the driving of separate areas of the eye-shield withseparate electronics channels such as that described in the co-pendingU.S. patent application Ser. No. 13/397,691, Publication No:US2013/0212765A1, to Cornelius (the “PWM Application”).

In another embodiment of the invention, each conductive region isprovided as being contiguous with adjacent regions of heating materialon the eye-shield. This embodiment of the invention enables a designerand manufacturer to produce eye-shields that either heat evenly, or heataccording to a profile, with or without a PWM control, and thus thisembodiment of the invention simplifies the manufacturing of a goggle,thus allowing for a less costly goggle.

In connection with either embodiment of the invention described above,the eye-shield in accordance with this aspect of the invention mayfurther comprise at least two bus bars connected to the conductiveregions and adapted for interconnecting the conductive regions with thepowered circuit. This embodiment of the invention allows a designer andmanufacturer of eye-shields to work with a single channel circuitprovided in a goggle. Alternatively, in either embodiment of theinvention, the eye-shield in accordance with this aspect of theinvention may further comprise a plurality of conductive bus-barsconnected to each of said conductive regions and adapted forinterconnecting each said conductive region with the powered circuit.This embodiment of the invention allows a designer and manufacturer ofheated eye-shields to work with a multichannel circuit to provide evengreater control over heating of the eye-shield.

In accordance with either aspect of the invention, and with any of theembodiments of the invention, the specified resistivity of the heatingmaterial may be either varied in accordance with varying formulations ofheating material, for example 10-ohm per square ITO (or other heatingmaterial), 20-ohm per square ITO, etc., or the thickness of the heatingmaterial may be varied to vary this resistivity. Or, alternatively, somecombination of varied formulation and varied thickness of heatingmaterial may be employed in accordance with either aspect of theinvention. Thus, in accordance with either aspect of invention and anyof the embodiments of the invention, the heating material of at leastone of the plurality of conductive regions of the eye-shield may beprovided to have a specified resistivity per square that is differentfrom the specified resistivity per square of the heating material ofanother of the plurality of conductive regions of the eye-shield.Further, the formulation of the heating material of at least one of theplurality of conductive regions may be selected in accordance with agiven resistivity per square for the heating material. Still further,the resistivity per square of the heating material of at least one ofthe plurality of conductive regions may be determined at least in partby varying the thickness of application of the heating material to thesubstrate. In this way, the designer and manufacturer of eye-shields isenabled greater flexibility to design the eye-shield and its desiredheating characteristics, whether with or without a heating profile, byselecting from available materials and thicknesses in accordance witheither aspect or any embodiment of the invention. Such flexibility ofdesign options for the eye-shield during design and manufacture makesbalancing of power densities across the plurality of conductive regionseasier to accomplish given size, shape, voltage input and power densityrequirements.

Also, regarding the eye-shield having a customized heating aspect and/orembodiment of the invention (whether in an electrically-isolated heatingregions embodiment or a contiguous heating regions embodiment), it willbe apparent from the foregoing that there may be provided at least oneregion of the plurality of conductive regions having a power densitythat is different than the power density of another of the plurality ofconductive regions. Thus, custom heating profiles may be more easilyenabled by employing one, or more, conductive regions of differentresistivity per square than another, or others, or differing thicknessesof conductive regions, or heating elements, on the same eye-shield, toaccommodate particular needs, such as extreme condition performancerequirements, custom applications, highly irregular-shaped eye-shields,and the like.

In accordance with another aspect of the invention, for all embodimentsof the invention and whether an even heating or a custom heating profileis used, the substrate of the eye-shield is preferably of an irregularshape, since it is such eye-shields that would otherwise be prone touneven heating. In this context, the term irregular shaped eye-shield,or substrate, means an eye-shield or substrate of any shape other thansquare or rectangular.

Thus, in accordance with an aspect of the invention, there is providedan eye-shield adapted for use with a powered circuit having a givenvoltage, for preventing fogging of the eye-shield and for preventing hotspots on the eye-shield, comprising: An optically-transparent substrateadapted for protecting a user's eyes and adapted for defining at least apartially-enclosed space between the user's eyes and said substrate; anda plurality of electrically-isolated conductive regions ofoptically-transparent electrically-resistive thin-film conductiveheating material on the substrate, wherein the power density of eachregion is the same as the power density of each other region and whereinthe heating material of at least one of the plurality of conductiveregions has a specified resistivity per square that is different fromthe specified resistivity per square of the heating material of anotherof the plurality of conductive regions.

Or, alternatively, in accordance with an alternative embodiment of anaspect of the invention, there is provided an eye-shield adapted for usewith a powered circuit having a given voltage, for preventing fogging ofthe eye-shield and for preventing hot spots on the eye-shield,comprising: an optically-transparent substrate adapted for protecting auser's eyes and adapted for defining at least a partially-enclosed spacebetween the user's eyes and the substrate; and a plurality of contiguousconductive regions of optically-transparent electrically-resistivethin-film conductive heating material on the substrate, wherein thepower density of each region is the same as the power density of eachother region and wherein the heating material of at least one of theplurality of conductive regions has a specified resistivity per squarethat is different from the specified resistivity per square of theheating material of another of the plurality of conductive regions.

Further, it will be appreciated from the foregoing that the resistivityper square of the heating material of the at least one of the pluralityof conductive regions may also be determined, at least in part, byvarying the thickness of application of the heating material to thesubstrate. Accordingly, it will be appreciated that the resistivity ofany region of heating material as part of the invention may be variedeither or both by choosing a heating material having a differentformulation and by varying the thickness of the application of theheating material to the lens substrate.

An eye-shield in accordance with an aspect of the invention provides aunique fog-prevention eye-shield for use in connection with ski goggles,dive masks, motorcycle helmet visors or snowmobile helmet visors, andthe like. Further an eye-shield in accordance with an aspect of theinvention provides a unique fog-prevention eye-shield for use inmedical, high-tech, testing or other working environments where foggingof a visor or eye-shield may become a problem. The elimination ofundesirable hot spots on the eye-shield is accomplished with an aspectof the invention in that each region may be designed to an appropriatesize and shape that yields a power density that is appropriate for thesize of the region being heated. And while a device in accordance withan aspect of the invention enables prevention of fogging while alsopreventing hot spots on the eye-shield without the need for apulse-width modulated (PWM) system as described in the PWM Application,the device also may be used in connection with such a PWM system if sodesired for other reasons. Thus, an eye-shield device in accordance withat least one aspect of the invention accomplishes heating of theeye-shield, and thus prevention of fogging while also preventing hotspots on the eye-shield in that the balancing of the heating of theeye-shield, or conversely customized zone heating of the eye-shield, isdetermined by the eye-shield itself and at the time of design andmanufacture. This makes provision of the eye-shield, and the resultinggoggle, mask or other eye-shield, more cost effective to produce andmore functionally efficient in preventing fogging and hot spots on theeye-shield, since less complicated and less expensive electronics areable to be used to produce the eye-shield and hence the resulting eyewear.

The foregoing aspects of the invention provide an eye-shield that isadapted for being heated in an electrical circuit to raise thetemperature of preferably an inner surface of the eye-shield above thedew point in order to prevent fogging, without creating undesirable hotspots in portions of the eye-shield, e.g., over the bridge of the nose,where a unitary evenly-applied heating material would produce too muchpower for the region causing it to overheat. Further, with the use ofPWM to maximize efficiency of the system as disclosed in the PWMApplication, the foregoing benefits and properties are able to beaccomplished by powering the eye-shield with a single, highly-portablepower source, such as a lithium-ion battery retained in the frame orstrap of the goggle. However, with the aid of one or more aspects of thepresent invention, a simple circuit consisting of one or more batteries,such as lithium-ion batteries, and an on/off switch, would be sufficientto provide a fog-free goggle lens that is either evenly heated acrossthe entire lens, or alternatively, is heated according to a customizedpattern.

The device of an aspect of the invention enables balanced, oralternatively customized, heating of the eye-shield with, or without, apulse-width modulated (PWM) heater driver as described in the PWMApplication. Thus, a device in accordance with an aspect of theinvention provides an eye-shield that is easy and cost effective toproduce, and the eye-shield will also function to allow even orcustomized heating with a variety of different heated goggles, masks orvisors. While a PWM heater driver like that disclosed in the PWMApplication would allow variability of the output of the heatingmaterial on the eye-shield and would allow even greater efficiency ofthe system in terms of battery usage, a PWM heater driver is notnecessary for achievement of certain aspects of the invention, since ifa user simply desires an even or customized heating profile of theeye-shield, without the ability to vary the heat output of theeye-shield as possible to conserve energy with a single-PWM channelheater driver, the user may simply use a constant voltage, constantoutput, heating system for the eye-shield of the invention to achievethe desired result. Thus, the invention may be adapted for use inconnection with an eye-shield heating system utilizing a portablebattery, as in the case of smaller batteries carried on a goggle body orstrap, or also if a larger battery is available, as in the case of abattery on a snowmobile, airplane, automobile or other vehicle.

With any embodiment of any aspect of the invention, there may be applieda nonconductive protective coating over the heating material to protectthe heating material. This protective coating secured to the heatingmaterial and the substrate helps ensure that the heating material willnot be damaged, as with scratching, which could impair the functioningof the heating material on the eye-shield.

Any of the aspects of the method for making an eye-shield of the presentinvention, or the resulting eye-shield of the present invention, may beadapted for use in connection with the manufacture of a sport goggle orany protective eye-shield, such as for skiing, inner-tubing,tobogganing, ice-climbing, snow-mobile riding, cycling, running, workingwith patients, in other medical or testing environments, and the like.Further, any of the aspects of the invention may be adapted for use inthe production of a diving mask eye-shield.

In accordance with another aspect of the invention, there is provided aneye-shield condensation prevention system which comprises an eye-shieldadapted for protecting a user's eyes, the eye-shield having a surfacearea divisible into at least one region for facilitating region heatingof the eye-shield to a desired temperature, a power source, at least onepulse-width modulator, at least one microcomputer, and at least oneheating element. The at least one heating element is located on andcorresponds with the at least one region, which will facilitate regionheating of the eye-shield. The at least one heating element correspondswith the at least one pulse-width modulator. The eye-shield condensationpreventing system in accordance with this aspect of the inventionfurther comprises a sensing circuit, also known as a micro-sensingcircuit, for comparing voltage sensed from the power source and heatingelement resistance voltage. The eye-shield condensation preventingsystem of this aspect of the invention further comprises at least onecircuit that interconnects the power source, the at least onepulse-width modulator, the at least one microcomputer, the at least onecorresponding heating element for heating the eye-shield and the sensingcircuit. The at least one microcomputer relays information to the atleast one pulse-width modulator that controls current. Controlling thecurrent controls and maintains the temperature of the at least oneheating element region to a temperature above an anticipated dew pointof an operating environment, thus alleviating dew and condensation fromthe eye-shield. The microcomputer determines heating element resistancefrom the sensing circuit and adjusts the pulse-width modulator's controlof current to the heater. Using the pulse-width modulator to control thecurrent flowing to the heater of the eye-shield addresses the problem ofvariable heater resistances of thin-film heaters from one region of aneye-shield to another, or from one eye-shield to another, bycompensating for variations in resistance that might otherwise beencountered from one of one eye-shield region to another eye-shieldregion and one eye-shield to another eye-shield. This aspect of theinvention counteracts the effects of uneven application of thin-filmheating elements, and varying resistances between different areas of aneye-shield and varying resistances from one eye-shield to anothereye-shield.

In accordance with this aspect of the invention, the eye-shieldcondensation prevention system may comprise a plurality of pulse-widthmodulators corresponding to a plurality of eye-shield regions and acorresponding plurality of heating elements of a goggle lens. Whencorresponding a plurality of heating elements with a plurality ofpulse-width modulators, the eye-shield condensation prevention systemadjusts at least one of the pulse-width modulators' control of currentto a corresponding eye-shield region and heating element. Thisadjustment of current compensates for variations in resistance ondifferent areas of an eye-shield, or variations in resistance from oneeye-shield to another eye-shield, as determined, for example, in testingof a batch of eye-shields.

Alternatively, in accordance with this aspect of the invention, theeye-shield condensation system further comprises a look-up table ofheating element resistance values each associated with a correspondingplurality of pulse-width adjustment factors. This table facilitatescalculations by the microcomputer for an appropriate adjustment to beapplied to the at least one pulse-width modulator. This adjustment bythe microcomputer compensates for variations in resistance encounteredfrom at least one of one eye-shield region to another eye-shield regionand one eye-shield to another eye-shield.

Still further, alternatively, in accordance with this aspect of theinvention, there is provided a plurality of eye-shield condensationprevention systems, wherein a first of the eye-shield condensationprevention systems is used to enable pulse-width modulator duty cycleadjustments to maintain constant heat from at least one heating elementof the first of the plurality of eye-shield condensation preventionsystems relative to the at least one heating element of a second of theplurality of eye-shield condensation prevention systems, despitevariations of heater resistance values from the first eye-shieldcondensation prevention system and the second eye-shield condensationprevention system. This aspect of the invention provides for consistentheating to be applied, despite variations in thickness of a thin-filmheating element that is applied to the eye-shield, from one eye-shieldregion to another eye-shield region, and one eye-shield to anothereye-shield. This aspect of the invention also addresses the issue of hotspots that occur on an eye-shield due to inconsistent thicknesses andresistances of a thin-film heating element, allowing for consistentheating across the entire surface of a goggle eye-shield by adjustingthe overall amount of power that is supplied to an eye-shield. Thisallows for greater user control over the goggle eye-shield, letting theuser set a temperature or setting that is consistent from one eye-shieldto another eye-shield.

The subject matter of the present invention is particularly pointed outand distinctly claimed in the concluding portion of this specification.However, both the organization and method of operation, together withfurther advantages and objects thereof, may best be understood byreference to the following descriptions taken in connection withaccompanying drawings wherein like reference characters refer to likeelements.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow chart regarding a method for adapting an eye-shield foruse in a system for preventing fogging of the eye-shield whilepreventing hot spots on the eye-shield in accordance with an aspect ofthe present invention;

FIG. 2 is a graphic representation front view of at least a portion ofan eye-shield having a plurality of equally-sized, electrically-isolatedheating material regions on a regular-shaped lens substrate andconnected in parallel with a dc battery;

FIG. 3 is a graphic representation front view of an alternate embodimentof at least a portion of an eye-shield having a plurality ofequal-length, electrically-isolated heating material regions on anirregular-shaped lens substrate and connected in parallel with a dcbattery;

FIG. 4 is a graphic representation front view of the alternateembodiment of FIG. 3, but wherein the power to the eye-shield iscontrolled with a plurality of corresponding pulse-width modulatedheater drivers;

FIG. 5 is a graphic representation front view of another alternateembodiment of at least a portion of an eye-shield having a plurality ofdifferent-sized (in plan view), electrically-isolated heating materialregions on an irregular-shaped lens substrate and connected in parallelwith a dc battery via a single pulse width modulator using a singleupper bus bar and a single lower bus bar;

FIG. 6 a is a graphic representation front view of another alternateembodiment of at least a portion of an eye-shield having a plurality ofdifferently-sized (in plan view), electrically-isolated heating materialregions on an irregular-shaped lens substrate and which may either haveheating material regions of equal thickness or different thicknesses;

FIG. 6 b is a graphic representation bottom view of the alternateembodiment of the portion of heated eye-shield shown in FIG. 6 a(assuming varied thickness heating element regions in FIG. 6 a), whereineven heating across the plurality of electrically-isolated heatingelement regions on the lens substrate is assumed and accomplished byapplying different thicknesses of the same transparent thin-filmconductive material to the lens substrate;

FIG. 6 c is a graphic representation bottom view of the alternateembodiment of the portion of the heated eye-shield shown in FIG. 6 a(assuming varied thickness heating element regions in FIG. 6 a) whereincustom heating (i.e., cooler in the center and hotter at each end)across the plurality of electrically-isolated heating element regions onthe lens substrate is assumed and accomplished by applying differentthicknesses of the same transparent thin-film conductive material to thelens substrate;

FIG. 7 a is a graphic representation front view of another alternateembodiment of at least a portion of an eye-shield having a plurality ofdifferent-sized (in plan view), contiguous heating material regions onan irregular-shaped lens substrate and which may either have heatingmaterial regions of equal thickness or varied thickness;

FIG. 7 b is a graphic representation bottom view of the alternateembodiment of the portion of heated eye-shield shown in FIG. 7 a(assuming varied thickness heating element regions in FIG. 7 a), whereineven heating across the plurality of contiguous heating element regionson the lens substrate is assumed and accomplished by applying differentthicknesses of the same transparent thin-film conductive material to thelens substrate;

FIG. 7 c is a graphic representation bottom view of the alternateembodiment of the portion of the heated eye-shield shown in FIG. 7 a(assuming varied thickness heating element regions in FIG. 7 a) whereincustom heating (i.e., cooler in the center and hotter at each end)across the plurality of contiguous heating element regions on the lenssubstrate is assumed and accomplished by applying different thicknessesof the same transparent thin-film conductive material to the lenssubstrate; and

FIG. 8 is a schematic representation of another alternate embodiment ofan eye-shield having a plurality of electrically-isolated heatingmaterial regions on an irregular-shaped lens substrate and using aplurality of upper bus bars, and a single lower ground bus bar, forconnecting each of the heating material regions with a multichannelcircuit, as with a multichannel PWM-controlled goggle circuit.

FIG. 9 is a schematic representation of an embodiment of a voltage andcurrent sensing, single-pulse-width modulator (PWM), current adjusting,single-region eye-shield fog prevention system in accordance with anaspect of the invention; and

FIG. 10 is a two-dimensional look up table employed with a microcomputer(MCU) that creates a mapping of PWM adjustment factors to heatingelement resistance values.

DETAILED DESCRIPTION

Referring to FIG. 1, a method 100 starting at origination location 102for adapting an optically-transparent eye-shield for use in anelectrical circuit to prevent fogging of the eye-shield while preventinghot spots on the eye-shield is disclosed. The method 100 comprises thefollowing steps after starting at 102: selecting a nonconductivesubstrate at 104 defining an optically-transparent eye-shield and anouter periphery of the eye-shield; determining the power source voltageat 106, which is preferably a dc battery voltage source (e.g., 8.4 VDCwhich is the output of two 4.2 VDC, fully-charged, lithium-ion cells),but which may also be an output from a PWM driver; determining a heatingprofile, if any, for defining a heating pattern within the outerperiphery of the eye-shield; determining at 108 the design, that is, thenumber of a plurality of regions and the size of each region (whetherelectrically-isolated or contiguous) in accordance with the heatingprofile; selecting at 110 a desired power density (Pd) for each region;mapping at 112 the heating regions onto corresponding regions of theeye-shield substrate; calculating the resistance per square (R) for eachregion using the formula R=(E²−Pd)/H² where R=resistance per square,E=voltage, Pd=power density and H=the distance between the bus bars(expressed herein as H since it is the distance vertically, as inheight, between upper and lower bus bars); applying 116 the heatingmaterial with corresponding resistance per square to correspondingconductive regions of the eye-shield to make each of the correspondingregions of the eye-shield adapted for conducting electricity; andapplying at 118 bus-bars connected to the regions adapted for conductingelectricity, the bus-bars and regions adapted for conducting electricityadapted to complete the electrical circuit powered by the battery. Itwill be appreciated that a plurality of upper bus bars and a singlelower bus bar may be used, as shown and further described below inconnection with FIG. 8, or a single upper bus bar and single lower busbar may be used, as shown and further described below in connection withFIG. 5. It will be appreciated that there are several different ways ofapplying heating material, such as ITO, to a substrate, includingcommonly known methods of ion sputtering, coating, vacuum depositedcoating, spraying, adhesive, adhesive backed and other methods.

An additional step of the process for creating a heated lens inaccordance with present invention, may involve application of anonconductive protective coating over the heating material to protectthe heating material on the substrate. Thus, a protective coating issecured to the heating material and the substrate to help ensure thatthe heating material will not be damaged, as with scratching, whichcould impair the functioning of the heating material on the eye-shieldsubstrate.

The eye-shield substrate (e.g., 212 of FIG. 2, 312 of FIG. 3, 602 ofFIG. 6 a, 702 of FIG. 7 a, or 800 of FIG. 8) may be selected 104 fromany of a number of materials, such as optically-transparentpolycarbonate, other plastic, tempered glass, and the like, that arerigid enough to screen a user's eyes from such things as snowfall, rain,wind or other relatively small airborne particles in the user'senvironment. In the case of ski goggles, or other cold weather goggles,preferably the eye-shield substrate (e.g., 212 of FIG. 2, 312 of FIG. 3,602 of FIG. 6 a, 702 of FIG. 7 a, or 800 of FIG. 8) is flexible enoughto generally conform to the user's head and face with the eye-shieldpreferably being retained in a semi-flexible frame that holds theeye-shield around its periphery and also holds the eye-shield, via theuse of a conventional strap, an appropriate distance from the user'sface so as to form an enclosed space around and in front of the user'seyes, the frame typically providing a semi-permeable seal between theuser's face and the rest of the goggle. Materials used for the variouseye-shields employed with the present invention should also be resistantto shattering, cracking or otherwise breaking as necessary for theparticular purpose for which they are chosen and as is known to those ofordinary skill in the art.

In the case of a dive mask, the eye-shield substrate (e.g., 212 of FIG.2, 312 of FIG. 3, 602 of FIG. 6 a, 702 of FIG. 7 a, or 800 of FIG. 8)will typically be selected 104 from a somewhat more rigid plastic, orglass, material, and in the case of a visor or medical full faceeye-shield the substrate would likewise be selected 104 of a somewhatmore rigid plastic, or glass, material that is sufficiently lightweight, but also sufficiently rigid to allow durable and repeatedpositioning of the eye-shield in place to protect the user's eyes.Selection 104 of the eye-shield substrate will preferably be of amaterial that is smooth to the touch, both on its inner (posterior)surface and its outer (anterior) surface and which is adapted to form abond with the selected heating material. Eye-shield substrate materialsare well known to those of ordinary skill in the art, and the selectionof any type of optically-transparent eye-shield substrate shall fallwithin the scope of the claims appended hereto.

Referring still to FIG. 1, the number of the plurality of regions andthe size of each region on the substrate may, or may not, be made inaccordance with a heating profile. A heating profile could be simply adesire, thought or understanding on the part of the designer of the lensthat even heating, to the degree feasible, across the lens substrate isdesirable. Or, alternatively, a heating profile may involve customheating of an eye-shield, as for example may be the case for asnowboarder as compared to a skier heating profile. Thus, a more formalheating profile may be used where one or more parts of the eye-shieldare to be intentionally made warmer than other parts of the eye-shield(e.g., where one side is warmer than another, or the edges are warmerthan the middle of the eye-shield), as opposed to simply even heatingacross the eye-shield. Thus, for example, in the case of a snowboarder,one side of the lens corresponding to the forward foot of thesnowboarder may require more heat since the snowboarder typically standsmore sideways while going down a hill. Whether even heating or customheating is contemplated, a heating profile may include a more detailedwritten profile including one or more of defined lens heating materialregions, identification of size and shape of lens heating materialregions, desired regions of relative increased heating, or decreasedheating, and identification or calculation of respective region powerdensities. Thus, the heating profile may be very simple, even justunderstood, or more complex and even written. A heating profiledetermines whether balanced, or even, heating is desired from oneconductive region to the next across the eye-shield, or whether a customprofile of full or proportional heating for each of the regions would bemore desirable for a given eye-shield configuration or purpose. Theinvention may be used to produce both regular and more irregular-shapedeye-shields that are evenly heated, or alternatively in accordance witha custom heating profile.

Referring now specifically to FIGS. 2-8, a progression, of less complexto more complex, of differing embodiments of the invention is shown toillustrate the many possible combinations of heating region sizes andshapes to accommodate differing sizes and shapes of substrates,differing methods of powering an eye-shield (e.g., dc battery and PWM),differing formulation and thicknesses of heating materials, differingapplications (e.g., electrically-isolated and contiguous), andincreasingly refined subdivisions of substrate to generalized heating orspecific multichannel PWM systems. It will be appreciated that therewill be other combinations of the foregoing basic elements to form aheated eye-shield lens which would not depart from the scope and spiritof the invention as set forth in the claims portion of thisspecification. For example, while the power source is shown in thepresent invention as coming from the top of the lens, with bus barsabove and beneath the lens, it will be appreciated by those of ordinaryskill in the art of electronics design that the power source may comefrom either side of the lens, or from the bottom of the lens, withoutdeparting from the true scope and spirit of the invention as claimed.

Referring specifically to FIG. 2, there are shown three equally-sized,rectangular, electrically-isolated heating element regions A, B and C(214, 216, 218 respectively) on a regular (rectangular-shaped)eye-shield 212, powered from the top with an 8.4 volt direct current(VDC) voltage source 202 via parallel circuitry 204, 206, 208, 210 andgrounded at 226 from the bottom via parallel circuitry 220, 222, 224.Each of these regions A, B and C have identical heating elementcoatings, such as formulated with the same resistivity (e.g., all mayemploy 20-ohm per square resistivity formulation of heating material)transparent and electrically conductive thin film heaters, such as ITO,zinc indium oxides (ZIO), zinc tin oxides (ZTO) or double-walled carbonnanotubes (DWNT). In FIG. 2, a simple version of an evenly-heatedembodiment of the invention is shown wherein the power density (Pd) forthese regions will be the same since each region is the same size,thickness and chemical formulation. Given a resistivity per square (R)of 20 ohms, we can calculate the power density of each region with thefollowing formula:Pd=E ² /R·H ²,where Pd is the power density, E is the voltage, R is resistance persquare, and H is the height (distance between bus bars).

Adding values to this formula yields the following result:8.4²/20·3²=0.392 watts per square=Pd. Again, this power density would bethe same for each of the regions, and since all of the other foregoingfactors would be equal (e.g., formulation of heating material, thicknessof heating material and height of the heating material) the eye-shield212 would be evenly heated across the entire eye-shield. Interestingly,by looking at the formula for power density, the distance L does notplay a role, such that even if A, B and C were merged together into asingle heating element, the power density would still be the same(assuming equal input voltage, equal H values, formulation of heatingmaterial, and thickness of heating material). Thus, in this simple caseof a regular-shaped substrate, while a single heating element may beemployed to achieve the same result, FIG. 2 illustrates that segmentingthe heating element into multiple regions opens up the option of heatingeach region separately, as with separate batteries or with PWM channelcontrols per the Cornelius patent application Ser. No. 13/397,691,Publication No. US2013/0212765A1 (the “PWM Application”). Further, sinceeven heating is not as difficult to achieve with thin-film heatingelements on a rectangular or square substrate, FIG. 2 represents thesimplest case for application of the invention of applying a pluralityof heating elements to a single eye-shield substrate.

Further, no bus bars are shown in FIG. 2, illustrating the fact that, inaccordance with the invention, the bus bars may either be on theeye-shield lens 212 itself, or housed in a goggle frame (not shown),depending upon the desired configuration of the eye wear.

Referring now specifically to FIG. 3, there is introduced the addedcomplexity over that shown in FIG. 2, of an irregularly-shaped substrate312 requiring that the three electrically-isolated regions A, B, C(respectively 314, 316, 318) are not of equal height, but rather havebeen adjusted to fit the trapezoid-shaped substrate 312. Such anembodiment, without the invention, is of the type that would have begunto introduce uneven heating, because of an irregularly-shaped eye-shieldsubstrate 312, into an eye-shield device. The embodiment of FIG. 3illustrates that the higher the H value of the heating element materialA, B, C (314, 316, 318), the lower the power density Pd. Thus, given aconsistent resistivity per square (R) of 20 ohms, because of thedifferent shapes A, B, C for covering the trapezoid-shaped substrate312, the power density calculations yield different results as follows:

A: Pd=E²/R·H² adding values: 8.4²/20·3²=0.392 watts per square

B: Pd=E²/R·H² adding values: 8.4²/20·3.6²=0.272 watts per square

C: Pd=E²/R·H² adding values: 8.4²/20·4.2²=0.200 watts per square

Thus, it can be seen that the shapes having a greater height (i.e.,region C, 318), where other factors (input voltage, heating materialthickness and resistivity formulation of heating material) are equal,have a lower power density (e.g., at 0.200 watts per square) than othershapes having a shorter height (H). The lower the power density of anarea, the cooler that area will operate given same voltage input.Conversely, shapes having lesser height (i.e., shape A, 314), whereother factors (such as input voltage, heating material thickness andresistivity of heating material) are equal, have a higher power density.Thus, since there has been a tendency for less high areas to becomeoverheated, such as region A in this embodiment, segmenting the areasand designing a power density profile in accordance with a desiredprofile, whether even heating across the substrate, or custom heating,is advantageous because a designer and manufacturer of eye-shields mayvary the formulation of heating material chosen, thickness of heatingmaterial applied, or height of a heating element in designing a lensaccording to desired parameters as shown and described later inconnection with FIGS. 5-8.

It should be noted in connection with FIGS. 2-8, that the inventioncomprises a plurality of different embodiments of eye-shields rangingfrom simple to more complex. As an example of a more simple eye-shieldin accordance with the invention, referring now to FIG. 3, each of theformulations of the areas A, B, C (314, 316, 318, respectively) isassumed to be of the same resistivity formulation material (20-ohms persquare at 800 angstroms thick), the same thickness and the same voltageapplied. Nevertheless, because of different heights (H) of the heatingelement regions, uneven heating of the regions of the embodiment of FIG.3 would occur without application of the invention. As with anyembodiment of the invention hereof, it will be appreciated that one mayvary the formulation or the thickness of the heating element in order toalter its resistivity and thereby massage the power density of a regionin accordance with a profile, whether it be even heating or customheating.

Further, it should be noted in connection with FIG. 3 that whileelectrically-isolated segments or regions A, B, C (314, 316, 318) havebeen shown, these regions are driven by a single power source 302 viaparallel circuit wires 306, 308, 310 and grounded at 326 via parallelcircuit wires 320, 322, 324. A single bus bar is implied (or converselymultiple bus bars may be used to bring power to and from the shownsingle power source), thus making this embodiment of the inventionsuitable for controlled heating with or without PWM controlled heating.It should be noted that contiguous segments A, B, C could have also beenemployed with similar results in the case of a single power source 302as shown.

Referring now specifically to FIG. 4, there is presented an embodimentof an eye-shield and substrate 414 that is similar to that of FIG. 3.However, in the embodiment shown in FIG. 4, there is specified athree-channel PWM circuit as shown in the PWM Application, comprisingPWM-1 402, PWM-2 404, PWM-3 406 for driving the eye-shield throughindependent connections 408, 410, 412 for heating regions A, B, C (416,418, 420, respectively). As with FIG. 3, each region A, B, C is of thesame resistivity per square, e.g., 20 ohms per square, but in thisembodiment, the amount of power to each region can be controlled bylimiting the PWM output therefore delivering less power to B, and evenless power to A, until both of those regions have the same power density(Pd) as that of C, to provide an evenly heated eye-shield. It should benoted that to achieve maximum balanced (even) power to all of theeye-shield regions A, B, C, the primarily available option is to limitthe power (via PWM in this embodiment) to regions B and A, since thoseregions are going to otherwise run hotter than C (assuming that C isrunning at full power).

Referring now to FIG. 5, there is shown an irregular-shaped substrate506 for an eye-shield having four electrically-isolated heating elementregions A, B, C, D (510, 512, 514, 516, respectively) thereon andpowered by a single-channel PWM (PWM-1) power source 502 via circuitwires 504 to a single upper bus bar 508 and a lower bus bar 518 toground wires 520. Using the formula R=(E²/Pd)/H² the resistance value(R) of each region may be calculated, and according to the followingassumptions, E=8.4 volts direct current (VDC), power density (Pd)=0.2watts per square, and the given heights (distance between bus bars,e.g., Ha=3.0, Hb=4.0, Hc=4.0 and Hd=2.5):

A: R=(E²/Pd)/H² adding values: R=(8.4²/0.2)/3²=39.2 ohms per square

B: R=(E²/Pd)/H² adding values: R=(8.4²/0.2)/4²=22.1 ohms per square

C: R=(E²/Pd)/H² adding values: R=(8.4²/0.2)/4²=22.1 ohms per square

D: R=(E²/Pd)/H² adding values: R=(8.4²/0.2)/2.5²=56.5 ohms per square

Thus, by applying the heating material based upon these calculations,there has been produced an eye-shield having even heating (i.e., equalpower densities) across the entire lens. This resistance per squareoutcome may be accomplished by selecting differing formulations ofheating material for the different heating elements, or alternatively,this may be accomplished by applying heating material of equalresistivity formulation in differing thicknesses to the heating elementregions in accordance with the calculations. Or, alternatively, theremay be employed a combination of both methods of varying theresistivity. Finally, if custom heating is desired, this may becalculated and accomplished as further specified in connection with FIG.6 below.

Referring still to FIG. 5, now that an evenly heated, balanced,eye-shield has been achieved, a single channel PWM may be used as shownto vary the input current to achieve desired levels of power densitiesfor the entire eye-shield. For example, if 50% power is desired evenlyacross the entire lens, then that may be accomplished with thisembodiment of the invention by setting the single-channel PWM 502 to a50% on, 50% off, setting. Thus, with this embodiment of the invention,multichannel PWM is not required to balance out the eye-shield regions,since this has been accomplished directly with the construction of theeye-shield and its heating elements. And, if on the other hand simply afull power application is preferable for a given eye-shield, the singlechannel PWM could simply be replaced with a single battery and an on/offswitch for providing on/off of full power evenly across the entire lenswith this embodiment of the invention.

Referring now to FIG. 6 a, an eye-shield substrate 602 is provided witheven more electrically-isolated heating element regions A-H than inprevious embodiments to enhance the degree to which the eye-shield maybe controlled and further enhancing the degree to which even heating orcustom heating may be accomplished across a still moreirregularly-shaped eye-shield. Thus, there is provided as shown in FIG.6 a an eye-shield having eight heating element regions: A, B, C, D, E,F, G and H (604, 606, 608, 610, 612, 614, 616, 618, respectively) withsize values as shown.

The resistivity of the heating element regions A-H of this embodiment ofthe invention have been normalized to provide even heating across theentire eye-shield substrate 602 either by using different thicknesses ofheating element material (e.g., ITO) applied to the substrate as shownin FIG. 6 b at 620, 622, 624, 626, 628, 630, 632, 634, or by usingdifferent resistivity formulations of heating material applied to thesubstrate (e.g., 10-ohm per square at 800 angstroms thick ITO, 20-ohmper square at 800 angstroms thick ITO, etc.). Finally, a combination ofthese methods may be employed. Note that a thicker application of thesame ITO material tends to decrease the resistivity of the material on aregion as compared to a thinner application.

Alternatively, the resistivity of the heating element regions A-H ofthis embodiment may be customized as shown in FIG. 6 c to provide lesserheating in the center of the eye-shield (e.g., at regions C-F) andgreater heating on the outside of the eye-shield (e.g., at regions A-Band G-H)—or according to some other custom profile. As shown in FIG. 6c, this is accomplished by changing the thickness of each region 636,638, 640, 642, 644, 646, 648, 650, 652 of the eye-shield to vary theresistivity of that portion of the eye-shield. Alternatively, this maybe accomplished by choosing different resistivity formulations ofheating material applied to the substrate (e.g., 10-ohm per square at800 angstroms thick ITO, 20-ohm per square at 800 angstroms thick ITO,etc.). Finally, a combination of these methods may be employed as well.

Thus, it may be appreciated that, whether an evenly-heated embodiment ofthe eye-shield is desired, or a customized heated embodiment of theeye-shield is desired, the desired result may be achieved by varying theresistivity of different segments of the eye-shield by varying thethickness, by choosing a different formulation of heating material, orby utilizing PWM heating channel technology as disclosed in the PWMApplication.

Thus, the embodiment shown in FIG. 6 a comprising regions A-H may havenormalized, or equalized, R values to balance power densities asdescribed above using, for example, one or both of formulation selectionand thickness application of heating material. Accordingly, oneadvantage illustrated by the embodiment shown in FIG. 6 a is that if,for example, a multichannel PWM heating source were to be used to varythe power density of the regions, the PWM system wouldn't have tocompensate for undesirable hot spots because the lens has already beennormalized. This, in turn allows for a greater range of control of theentire lens by the PWM, since part of the degree of adjustment availablewill not have been lost in compensating for overheating areas of theeye-shield. By way of example referring to FIG. 6 a, it might bedesirable to increase the number of regions to provide bettergranularity, or degree, of control of the heated areas on the eye-shieldas shown with varying resistivity values calculated (and able to beachieved as described above) as follows:

A: R=(E²/Pd)/H² adding values: R=(8.4²/0.2)/3²=39.2

B: R=(E²/Pd)/H² adding values: R=(8.4²/0.2)/3.7²=25.8

C: R=(E²/Pd)/H² adding values: R=(8.4²/0.2)/3.8²=24.4

D: R=(E²/Pd)/H² adding values: R=(8.4²/0.2)/4.2²=20.0

E: R=(E²/Pd)/H² adding values: R=(8.4²/0.2)/4.2²=20.0

F: R=(E²/Pd)/H² adding values: R=(8.4²/0.2)/3.8²=24.4

G: R=(E²/Pd)/H² adding values: R=(8.4²/0.2)/2.7²=48.4

H: R=(E²/Pd)/H² adding values: R=(8.4²/0.2)/2.2²=72.9

The foregoing resistivity per square values are calculated for evenheating across the entire substrate 602, and may be accomplished eitherby changing the effective voltage with PWM, or by changing theformulation or thickness of application of the heating material appliedas described above. Further, it will be appreciated that the greater thespecificity of regions, as for example shown and described in FIG. 8,the greater control over the lens that may be achieved and the greaterthe degree of evenness may be achieved across the entire lens.

Referring now to FIGS. 7 a-7 c there is provided part of an eye-shieldsubstrate 702 having a plurality of contiguous heating element regionsA-H (704, 706, 708, 710, 712, 714, 716, 718, respectively). Should agreater degree of even-heating specificity be desired on a giveneye-shield, for example for a highly-irregularly shaped eye-shield, butfor which nevertheless a simplified electronics system is desired, evenas simple as a single battery, the invention includes an embodiment suchas that of FIG. 7 a wherein a single upper bus bar 754, and a singlelower bus bar 756, may be used to connect with this plurality ofcontiguous heating element regions.

In FIG. 7 b, a balanced heating eye-shield or screen is shown wherein,similarly to FIG. 6 b, the even heating may be accomplished by one or acombination of varying the thickness of the heating material applied andselection of different formulations of heating material for differentareas. However, varying the thickness of the heating material for thepresent embodiment is preferable, since in this way a smoothertransitioning of variation of resistivity across the lens may beachieved without banding. Thus, FIG. 7 b illustrates an evenly heatingeye-shield comprising regions 720, 722, 724, 726, 728, 730, 732, 734,wherein the inner regions 724, 726, 728, 730 are thicker than the outerregions 720, 722, 732, 734 to provide normalized heating across theentire substrate similarly to that described previously in connectionwith FIG. 6 b. However, as shown in FIG. 7 b, the transitions betweenthe contiguous segments or regions of heating material are smoother,less stair-stepped, allowing for less contrast between regions and thussmoother power density transitions between regions. In other words, thepower densities of the contiguous embodiment of the eye-shield shown inFIG. 7 b are continuously variable.

In FIG. 7 c, there is shown a customized heated eye-shield having aplurality of contiguous heating elements 736, 738, 740, 742, 744, 746,748, 750, 752 wherein, similarly to FIG. 6C, the custom heating profileprovides for cooler segments in the middle areas 740, 742, 744, 746 andwarmer regions in the outer areas 736, 738, 750, 752. As described inconnection with FIG. 7 b, the power density transitions with thisembodiment are less stair-stepped and more continuously variable acrossthe eye-shield, thus providing smoother power density transition betweenthese contiguous regions. Also, as with the eye-shield of FIGS. 6 a-6 cand 7 a-7 b, the embodiment of the invention shown in FIG. 7 c may beaccomplished with a single power source, such as a single battery, or asingle channel PWM, driving the single bus bars 754, 756.

The figures illustrating embodiments of the invention shown in FIGS. 6b, 6 c, 7 b and 7 c are for illustrative purposes only. And while anattempt has been made to show relative differences in thickness ofapplication of heating material to scale, it will nevertheless beappreciated that since these thickness are on the order of hundreds ofangstroms thick, the drawings represent rough approximations of relativethickness of material, not actual to-scale representations.

Referring now to FIG. 8, there is shown an eye-shield substrate 800 thatis divided into even more, that is twenty four, heating regions, regions802, A-X, than previously-described embodiments. Preferably each ofthese heating regions 802, A-X has been normalized as described above inthat they either have even heating, or a desired custom profile. Thisembodiment of the invention clearly shows that over the bridge of thenose, the regions are less high (that is, they have a lesser value ofH), and thus they would traditionally be prone to overheating withoutthe present invention. Further, there are provided multiple channels a-xsuch that multiple PWM channels may be used, as described in the PWMApplication, to further specify and drive the eye-shield heating systemin a way that conserves battery life. Further, FIG. 8 illustrates theuse of a plurality of bus bars, one for each channel to enableindependent control of and power to each heating region 802, A-X, and asingle ground bus bar 806.

Because of the greater specified granularity of control provided withthe embodiment of the invention of FIG. 8, different detailed profilesmay be implemented, all with the same eye-shield, as driven by acomputer microprocessor contained within the goggle. Some examples ofthese profiles include a skier sunny-day profile, a snowboarder icingconditions profile, a rock climber raining conditions profile, a rescuepatrol profile, a snowmobiler profile and a dive mask profile, etc.

While preferred embodiments of the present invention have been shown anddescribed, it will be apparent to those skilled in the art that manychanges and modifications may be made without departing from theinvention in its broader aspects. For example, it will be appreciatedthat one of ordinary skill in the art may mix and match the variouscomponents of the various embodiments of the invention without departingfrom the true spirit of the invention as claimed. The appended claimsare therefore intended to cover all such changes and modifications asfall within the true spirit and scope of the invention.

Referring to FIG. 9, a single pulse-width modulator (PWM), single regionfog prevention system 900 is shown comprising a battery power source 902having positive and negative terminals 904, 906, circuit wires 908, 910,PWM 912 (which generates signal 914), MOSFET switch 916, eye-shield 918,heating element 920, a microcomputer (MCU) 922, a heater voltage senseresistor 924, a heater current sense resistor 926, a sense voltage 928,and a heater current voltage sense 930. A circuit 908, 910 interconnectsthe battery power source 902, the PWM 912, the MCU 922, the MOSFETswitch 916, the heater current sense resistor 926, the sense voltage928, the heater voltage sense resistor 924 and the heating element 920,the MCU 922 gathers information about the heater voltage sense resistor924 and determines the heating element 920 resistance. The MCU 922 thenrelays information based on the heating element 920 resistance to thePWM 912 in order to adjust current which the PWM 912 controls.Controlling the current will in turn help to maintain temperature of theheating element 920 from one eye-shield defogging system 900 to another,despite variations in heating element resistivity from one eye-shield tothe next, or from one eye-shield heating region to another, for exampleamong regions A-H of FIG. 6 a, regions A-H of FIG. 7 a, or regions A-Xof FIG. 8, to a temperature that is above an anticipated dew pointtemperature of an operating environment, despite variations in heatingelement resistivity from one region to the next.

Thus, although FIG. 9 is shown as a single PWM, single region fogprevention system, it will be appreciated that the invention may beapplied to eye-shields having more than one region, as has been shown inFIGS. 2-8, where there is a progression of less complex to more complexembodiments of the invention having more than one region on theeye-shield, in order to create uniformity, or consistently accuratepower densities for a custom heating profile, while heating eacheye-shield region relative to each other eye-shield region, despitevariations in resistivity of the heating elements of each of theregions. And, alternatively, the invention may be applied to ensure thatmultiple eye-shields have consistent properties as experienced by usersfrom one eye-shield to another eye-shield, despite variations inresistivity of the heating elements on each of the eye-shields. It willbe appreciated that there will be other combinations of the elements toform a heated eye-shield lens which would not depart from the scope andspirit of the invention as set forth in the claims portion of thisspecification.

In the embodiment of the invention shown in FIG. 9, the MCU 922 is shownas a device which comprises a potentiometer and has an internalreference voltage (vref) that is lower than the battery minimum usablevoltage and provides an output voltage (input voltage to the PWM 912),the output voltage from the MCU 922 being some voltage between zero andthe reference voltage (vref) based upon the setting of thepotentiometer. Responsive to the MCU 922, the PWM 912 produces acorresponding percentage on/off signal that can be varied as a result ofoutput from the MCU 922. In a preferred system using digital logic, acontrol MCU responsive to a MORE (increase) button and responsive to aLESS (decrease) button directly varies the duty cycle of the PWM 912 andthereby varies the amount of current delivered to the heating element920 without requiring an intermediate voltage reference.

An output line 932 carrying the output voltage of the MCU 922 isoperatively connected between the MCU 922 and the PWM 912. The PWM 912translates the output voltage from the MCU 922 into a signal having aduty cycle corresponding and proportional to the magnitude of thevoltage into the PWM 912. The duty cycle of the PWM's 912 output willtherefore vary in relation to the voltage in from the MCU 922 such thata near-zero input voltage from the MCU 922 to the PWM 912 will result ina near-zero percent on/near 100 percent off duty cycle output of the PWM912. By contrast, where the voltage in from the MCU 922 to the PWM 912is near the maximum voltage (vref) of the MCU 922, a resulting near 100percent on/near-zero percent off duty cycle output of the PWM wouldresult. Further, and accordingly, for each intermediate setting of theMCU 922 between minimum and maximum output voltage to the PWM 912, acorresponding intermediate percentage on/percentage off duty cycleoutput of the PWM 912 would result. Thus, the MCU 922 enables variedoutput duty cycles of the PWM 912.

The defogging ability of the heating element 920 is determined by theamount of power supplied to the heating element 920. Heating elementpower is a function of the voltage applied across the heating element920, the amount of time the voltage is applied to the heating element920 which is established by the duty cycle of the PWM 912, andelectrical resistance of the heating element 920. The heating elementpower is governed by the following equation:

${{Heating}\mspace{14mu}{Power}} = {\left( \frac{V^{2}}{R} \right)\left( \frac{{Duty}\mspace{14mu}{Cycle}}{100} \right)}$Where V is voltage, and R is heating element 920 resistance, and whereduty cycle is expressed as a percent of switching element “on time”.Therefore, as shown by this equation, actual heating power for heatingelement 920 in any given eye-shield 918 varies not just with voltage andduty cycle, but also with the resistance of heating element 920.

In order to maintain a consistent amount of power to the heating element920 from one eye-shield to the next, and thus maintain a constanttemperature of the heating element 920 from one eye-shield to the next,or one region of an eye-shield to another region of the same eye-shield,the duty cycle of the PWM 912 is increased or decreased to compensatefor varying resistances of the heating element 920. In order tocorrectly compensate for variations of heating element 920 resistance,the MCU 922 must first establish the actual value of resistance ofheating element 920. The MCU 922 first establishes the actual resistanceby monitoring and obtaining values for the sense voltage 928 through theheater voltage sense resistor 924 that is applied to the heating element920, and also monitoring the heater current sense voltage 930 that isapplied through the heater current sense resistor 926 that has a fixedresistance. The MCU 922 will do this whenever the PWM 912 is in the “on”state.

After monitoring and obtaining a value for the sense voltage 928 andheater current sense voltage 930, and already knowing a value for theheater voltage sense resistor 924, the MCU 922 then uses these voltagevalues and resistance values to determine the heating element resistanceusing the following equation.

${{Heating}\mspace{14mu}{Element}\mspace{14mu}{Resistance}} = \frac{{Heater}\mspace{14mu}{Current}\mspace{14mu}{Sense}\mspace{14mu}{Voltage}\mspace{14mu} 930}{\left( \frac{{Sense}\mspace{14mu}{Voltage}\mspace{14mu} 928}{{Heater}\mspace{14mu}{Voltage}\mspace{14mu}{Sense}\mspace{14mu}{Resistance}\mspace{14mu} 924} \right)}$

Now that the heating element resistance is known, the MCU 922 will relaya signal to the PWM to adjust the duty cycle by a multiplying factor,called a PWM adjustment factor. The PWM adjustment factor is derivedfrom the heating element resistance that is calculated by the MCU 922using the following equation:

${{PWM}\mspace{14mu}{Adjustment}\mspace{14mu}{Factor}} = \frac{{Heating}\mspace{14mu}{Element}\mspace{14mu}{Resistance}}{{Nominal}\mspace{14mu}{Resistance}}$where nominal resistance is a known and a desired value of resistancefor the heating element 920.

In the instance of this MCU embodiment of the invention, atwo-dimensional look-up table is employed, an example of which is seenin FIG. 10. The look-up table creates a mapping of PWM adjustmentfactors that relates to heating element resistance values. For example,in an eye-shield design where the nominal heating element 920 resistanceis ten ohms, where also there is a known variation of resistance fromone eye-shield to another eye-shield or one region of an eye-shield toanother region of the same eye-shield of plus or minus twenty percent,then a look-up might look as it appears in FIG. 10. Thus, if it isdetermined by an MCU 922 of the system of the invention that the heatingelement's 920 resistance is eight ohms, instead of the specified tenohms, the system would compensate for the variance by supplying a PWMadjustment factor of 0.80 as described previously in connection with thelook-up table of FIG. 10. On the other hand, a heating element 920resistance of twelve ohms would be compensated by the system with a PWMadjustment factor of 1.20. In this example of a two-dimensional look-uptable as shown in FIG. 10, the nominal value of the heating element 920resistance is ten ohms. However, other nominal resistances and measuredresistance ranges can be used, and PWM adjustment factors correspondingto other nominal resistances and measured resistance ranges are foundusing the equation for PWM adjustment factors.

In the two-dimensional look-up table as shown in FIG. 10, the number ofheating element resistances expressed in the table is variable, and isdependent upon the specificity with which PWM 912 adjustments should bemade for a given application. It might be desirable in somecircumstances to have a fine granularity of PWM adjustments so that theheating element 920 stays at a precise temperature. In anothercircumstance, a broad granularity of PWM adjustments might be moresuitable when consistent temperature is not necessary. In allcircumstances, this combination of heating element 920 resistancesensing and corresponding PWM 912 duty cycle adjustment allows theeye-shield heating element 920 to maintain constant heat, and theability to compensate for variations in resistance encountered from oneeye-shield region to another, and one eye-shield to another eye-shieldas may be determined, for example, by testing resistivity of a batch ofeye-shields.

While a preferred embodiment of the present invention has been shown anddescribed, as well as other embodiments of the invention, it will beapparent to those skilled in the art that many changes and modificationsmay be made without departing from the invention in its broader aspects.For example, it will be appreciated that one of ordinary skill in theart may mix and match various components of the embodiments of theinvention shown and described without departing from the true spirit ofthe invention as claimed. The appended claims are therefore intended tocover all such changes and modifications as fall within the true spiritand scope of the invention.

The invention claimed is:
 1. An eye-shield condensation preventionsystem comprising: an eye-shield adapted for protecting a user's eyes,said eye-shield having a surface area divisible into at least one regionfor facilitating region heating of said eye-shield to a desiredtemperature; a power source; at least one pulse-width modulator; atleast one microcomputer; at least one heating element on andcorresponding with the at least one region for facilitating regionheating of said eye-shield, said at least one heating elementoperatively connected to and corresponding with said at least onepulse-width modulator; a sensing circuit for comparing voltage sensedfrom said power source and heating element resistance voltage; and atleast one circuit interconnecting said power source, said at least onepulse-width modulator, said at least one microcomputer, said at leastone corresponding heating element for heating said eye-shield and saidsensing circuit, wherein said at least one microcomputer relaysinformation to said at least one pulse-width modulator that controlscurrent to maintain the temperature of said at least one heating elementregion to a temperature above an anticipated dew point of an operatingenvironment, said microcomputer determining heating element resistancefrom said sensing circuit and adjusting said pulse-width modulator'scontrol of current to said heater to compensate for variations inresistance that might otherwise be encountered from at least one of oneeye-shield region to another eye-shield region and one eye-shield toanother eye-shield.
 2. The eye-shield condensation prevention system ofclaim 1, wherein said eye-shield condensation prevention systemcomprises a plurality of pulse-width modulators corresponding to aplurality of eye-shield regions and a corresponding plurality of heatingelements of a goggle lens, and wherein said eye-shield condensationprevention system is used to adjust at least one of said pulse-widthmodulators' control of current to a corresponding eye-shield region andheating element.
 3. The eye-shield condensation prevention system ofclaim 1, wherein said eye-shield condensation system further comprises alook-up table of heating element resistance values each associated witha corresponding plurality of pulse-width adjustment factors tofacilitate calculation by said microcomputer of an appropriateadjustment to be applied to said at least one pulse-width modulator tocompensate for variations in resistance encountered.
 4. The eye-shieldcondensation prevention system of claim 1, further comprising aplurality of eye-shield condensation prevention systems in accordancewith claim 1, wherein a first of said eye-shield condensation preventionsystems is used to enable pulse-width modulator duty cycle adjustmentsto maintain constant heat from at least one heating element of saidfirst of said plurality of eye-shield condensation prevention systemsrelative to the at least one heating element of a second of saidplurality of eye-shield condensation prevention systems, despitevariations of heater resistance values from said first eye-shieldcondensation prevention system and said second eye-shield condensationprevention system.